The crossword solution for the term 'Part of the Staircase' is 'STEP', which is a four-letter word. A STEP is a single, flat surface in a staircase that one steps on when ascending or descending. Steps are typically made of wood, metal, stone, or concrete and are usually connected to each other by a riser. Steps are an important part of any staircase, as they provide stability and support for the user.